import 'dart:io';

void main() {
  print('开始执行main函数');
  // print(getNetworkData());
  getNetworkData().then((value) {
    print(value);
  });

  print('这是不能被阻塞的代码');
}

Future<String> getNetworkData() {
  return Future<String>(() {
    sleep(Duration(seconds: 3));
    return '返回的网络数据';
  });
}